1. Field of the Invention
The present invention relates to a transmitter device that formulates data upon receipt of a request signal and transmits the formulated data to a receiver device via a wireless system or a wired system.
2. Description of Related Art
There are various transmitter devices that are activated by a battery and transmit data formulated according to a request signal via a wireless or wired system. One example is a transmitter device for use in a keyless entry system for an automotive vehicle. The transmitter device of the keyless entry system is powered by a battery and wirelessly transmits a locking or an unlocking signal to an on-board receiver. Another example is an on-board transmitter powered by an on-board battery for performing wired communication with various automotive electronic devices. Yet another example is a so-called remote controller used in home appliances such as a television set.
In those transmitter devices, there is a situation where power supply to the transmitter device is temporarily disconnected by an outside force applied thereto by a user, or a situation where a power source voltage temporarily drops due to heavy power consumption by other electrical loads. To cope with such a temporary power supply trouble, a large capacitor for storing power is usually used in a transmitter device.
The power-storing capacitor, however, cannot cope with a power supply trouble that lasts a considerable period of time. If the power source voltage drops to a certain level, incorrect data may be transmitted. In many conventional transmitter devices, operation of a transmission controller is stopped when the power source voltage drops to a predetermined level, and its operation is restarted upon recovery of the power source voltage. Therefore, data transmission may be discontinued in its middle. If this happens in the remote controller, an appliance cannot be operated in response to a request signal inputted by a user.
Though this kind of power source troubles may be avoided to a certain degree by increasing a capacity of a power-storing capacitor, the large capacitor requires a large space in the transmitter thereby making the transmitter bulky and costly.